Future Projection of Precipitation Changes in the Júcar and Segura River Basins (Iberian Peninsula) by CMIP5 GCMs Local Downscaling

Abstract

The basins of the Júcar and Segura rivers, on the Mediterranean coast of the Iberian Peninsula, present a special water problem and are of particular interest regarding climate change. These basins are very vulnerable to a possible scenario of decreasing water resources. Recent studies on historic rainfall since 1955 have indicated an ongoing loss of precipitation in their headwaters, especially in the case of the Júcar river. The aim of the present study is to perform climate projections for the precipitation variable for several future periods (2021–2040, 2051–2070, 2081–2100) and emission scenarios (RCPs 4.5, 8.5) within the Júcar and Segura River Basin authorities. For this purpose, a set of CMIP5 global models have been used, as well as the CDRD-HR-EIP-1955-2016 database, as a source of local observed information. This database comprises nearly 900 precipitation series in both basins and has been used in recent studies to determine historic trends of change in these basins. A statistical downscaling of the global models for all available observed series has been applied using the LARS-WG method. The results, although variable according to the CMIP5 model used, show the continuation of the patterns of precipitation change in the future, as already observed in the historical series. The results also predict a clear reduction in precipitation in the long term. However, torrential rainfall tends to increase in the coastal areas in relation to that observed in the short-term predictions. These results, due to their high spatial resolution, are of great interest for their use in small-scale hydrological and spatial planning (regional and local), which is one of the current challenges of climate modeling.

Climate change in two Mediterranean climate areas (Spain and Chile): evidences and projections

“…Water vapour transport seems to be a significant factor in the occurrence of extreme rainfall events when the moisture trajectories originate in the Western Mediterranean, an area with high SSTs, meaning a greater moisture supply. Meanwhile, the seasonality analysis reveals greater losses in precipitation are projected for spring and summer on the Spanish Mediterranean coast (Miró et al, 2021). In the two Mediterranean climate areas analysed, we can observe a trend towards prolonged drought periods.…”

“…Based on the analysis of the spatial and temporal variability of daily rainfall in Spain in the period 1950-2012 and on the high-resolution daily gridded data set, SPREAD at a spatial resolution of 5×5 km., Serrano-Notivoli et al (2018), find the following significant facts: 1) a slight global increase in the duration of the rainfall events, particularly along the Mediterranean strip; 2) an increase in the frequency of low rainfall events and a reduction in the frequency of high and very high events (inversed on the Mediterranean coast); and 3) a slight reduction in the intensity of unique events (duration of 1 or 5 days), but a significant negative trend in mean and median rainfall when considering all of the days of rainfall (p> 0), particularly on the Mediterranean coast. Miró et al (2021), in their study on the evolution of rainfall in the Jucar and Segura river basins, based on the use of CMIP% GCMS Local Downscaling, in an RCP 4.5 and 8.5 scenario and contemplating 900 rainfall series, indicate an increasing trend in the frequency of torrential rain episodes in the coastal areas of the field of study, as opposed to the considerable reduction in the headwaters of these rivers.…”

Precipitation and drought trends (1952–2021) in a key hydrological recharge area of the eastern Iberian Peninsula

“…• Summer and winter are the seasons most affected by reduced precipitation, with losses in some rainfall stations exceeding 120 mm between the two 35-year reference periods and, in some cases, with reductions of almost 50% for all the fallen rainfall. At the same time, climate projections tend to predict a significant reduction in rainfall for forthcoming years (Barcikowska et al, 2018;Grise et al, 2019;Miró et al, 2021;Zappa, 2019), mainly in the months of the abovecited seasons. The most affected basins are CHG and CHT, where 80% of the studied stations show a significant negative trend for rainfall evolution for the last 70 years.…”

Seasonal behaviour and influence of altitude on fog‐water collection in the Eastern Iberian Peninsula (2003–2012)

“…Of all the precipitation characteristics in this area, the following should be highlighted: (i) its torrentiality, which is more pronounced in places near the coast; (ii) its irregularity in space and time terms; (iii) the presence of long dry periods, especially in southern parts of the region in summer. In today's climate change context, recent studies estimate a general negative trend for precipitation in the selected area, mainly for the precipitation types that do not generate extreme intensities, which occur generally inland and are the most efficient in the maintenance of water reservoirs (Mill an et al, 2005;Mir o et al, 2017Mir o et al, , 2021. This area also has a high percentage of sunny days, which favours the formation of thermal winds, such as breezes (Azorin-Molina et al, 2009), and push moisture-laden air masses towards the coast, which favours the formation of orographic fog when faced with elevated reliefs (Azorin-Molina et al, 2010).…”

“…Several studies have demonstrated the following: a negative trend for precipitation in this region, which is more marked in summer months; slightly fewer days with precipitation; a longer maximum length for dry periods; a bigger fraction of precipitation falling in higher percentiles (less, but more intense precipitation) (Millán et al ., 2005; Mestre Guillem et al ., 2015; Miró et al ., 2018). Thus in this region, we expected to find the number of days with precipitation to drop and dry rainless periods to prolong (Miró et al ., 2021). In relation to this, another characteristic of the climate to the east of the Iberian Peninsula is the large number of days with no rain (<1 mm) or dry days.…”